This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We propose an innovative approach to the field of non-invasive monitoring of blood glucose and related variables, the detection and quantification of trace amounts of Volatile Organic Compounds (VOCs) in exhaled human breath as biomarkers endogenous metabolism. Exhaled gases represent an ideal set of potential biomarkers, as they can be collected easily and non-invasively from virtually any patient. While the potential of VOCs has been recognized for decades and several attempts have been made to utilize them for metabolic monitoring, intrinsic difficulties in measurement and analysis have resulted in inconsistent results, severely limiting their practical applicability. Recent advances in analytical technology, however, may have reduced, if not solved, these problems, and resulted in renewed interest in this methodology, with an exponentially rising number of studies focusing on its applications. Among the greatest contributors to these advances are Drs. Sherwood Rowland and Donald Blake, world renowned atmospheric chemists and co-investigators in this application (for his discoveries in atmospheric gas composition, Dr. Rowland was awarded the 1995 Nobel Prize for Chemistry).